Energy Storage

Question 1

which cells have an absolute requirement for glucose

Answer 1

RBCs, lens of the eye, medulla of the kidney and neutrophils

Question 2

at what glucose plasma level does death and brain damage result from

Answer 2

0.6 mmol/L

Question 3

what can be used in blood tests to determine plasma glucose levels

Answer 3

HbA1c

Question 4

what is glucose stored as

Answer 4

glycogen

Question 5

what does muscle glycogen supply

Answer 5

glucose to skeletal muscle cells

Question 6

what does liver glycogen supply

Answer 6

glucose to the body

Question 7

describe the structure of glycogen

Answer 7

there is a central protein glycogenin with glucose residues branching off linked by alpha-1,4 and alpha-1,6 glyosidic bonds

Question 8

what is glycogenesis

Answer 8

to production of glycogen

Question 9

outline glycogenesis

Answer 9

• glucose and ATP are converted into G6P and ADP by hexokinase
• G6P is converted into G1P by phosphoglucomutase
• G1P, UTP and H20 are converted into UDP-glucose by G1P uridylyltransferase
• UDP-glucose reacts with glycogen to add the glucose residue onto the glycogen molecule

Question 10

which 2 enzymes can add the glucose residue from the UDP-glucose onto the glycogen molecule

Answer 10

• glycogen synthase for alpha-1,4 bonds

- branching enzyme for alpha-1,6 bonds

Question 11

what is glycogenolysis

Answer 11

breakdown of glycogen

Question 12

outline glycogenolysis

Answer 12

• G1P is released from the glycogen by glycogen phosphorylase or de-branching enzyme
• G1P is converted into G6P by phosphoglucomutase

Question 13

true or false: glycogenolysis is the reversal of glycogenesis

Answer 13

false - different enzymes allow inhibition and stimulation of the different pathways

Question 14

what happens to the G6P produced by liver cells

Answer 14

converted into glucose and released into the blood for use by other tissues

Question 15

what happens to the G6P produced by muscle cells

Answer 15

used by muscle cells in glycolysis for energy production

Question 16

what enzyme in the liver converts G6P into glucose

Answer 16

glucose-6-phosphatase

Question 17

what is the rate limiting enzyme in glycogen synthesis

Answer 17

glycogen synthase

Question 18

what is the rate limiting enzyme in glycogen degradation

Answer 18

glycogen phosphorylase

Question 19

what hormone increases the activity of glycogen synthase

Answer 19

insulin

Question 20

what hormone increases the activity of glycogen phosphorylase

Answer 20

glucagon

Question 21

true or false: AMP is an allosteric activator of glycogen phosphorylase

Answer 21

true - but only in the muscles not in the liver

Question 22

give 2 examples of glycogen storage diseases

Answer 22

1. von Gierke’s disease

2. McArdle disease

Question 23

what is von Gierke’s disease

Answer 23

deficiency in glucose 6 phosphatase

Question 24

what is McArdle disease

Answer 24

deficiency in muscle glycogen phosphorylase

Question 25

what is gluconeogenesis

Answer 25

production of glucose

Question 26

what are the 3 major precursors of glucose

Answer 26

- lactate - glycerol - amino acids

Question 27

where does gluconeogenesis occur

Answer 27

liver (and also the kidney)

Question 28

in what cycle is lactate used in respiration

Answer 28

cori cycle

Question 29

outline the cori cycle

Answer 29

glucose is converted into lactate in muscle which then travels in the blood to the liver where its converted back to glucose

Question 30

what are the 3 key enzymes in gluconeogensis

Answer 30

- glucose-6-phosphatase - fructose 1,6-bisphosphatase - PEPCK

Question 31

what does glucose-6-phosphatase do

Answer 31

converts G6P into glucose

Question 32

what does fructose-1,6-bisphosphatase do

Answer 32

converts fructose 1,6-bisphosphate into G6P

Question 33

what does PEPCK do

Answer 33

converts oxaloacetate into phosphoenolpyruvate

Question 34

which hormone stimulates gluconeogensis

Answer 34

glucagon and cortisol

Question 35

which hormone inhibits gluconeogenesis

Answer 35

insulin

Question 36

what are lipids stored as

Answer 36

triacylglycerides

Question 37

where are triacylglycerides stored

Answer 37

in adipose tissue

Question 38

when are triacylglycerides used for energy

Answer 38

in prolonged exercise, pregnancy, stress and starvation

Question 39

what enzyme breaks down triacylglycerides

Answer 39

pancreatic lipases

Question 40

what are triacylglycerides broken down into

Answer 40

fatty acids and glycerol

Question 41

what happens to the fatty acids and glycerol in intestinal epithelia cells

Answer 41

they are reformed to TAGs then converted into chylomicrons where the enter the lymph system

Question 42

where do the chylomicrons drain into the blood

Answer 42

left subclavian vein

Question 43

what hormone mobilised TGA metabolism

Answer 43

glucagon and adrenaline

Question 44

what hormone inhibits the metabolism of TGAs

Answer 44

insulin

Question 45

what happens to the TGAs in the blood

Answer 45

they can either be stored in adipose tissue or used in fatty acid oxidation

Question 46

what is lipogenesis

Answer 46

fatty acid synthesis

Question 47

where does lipogenesis occur

Answer 47

liver

Question 48

outline lipogenesis

Answer 48

- pyruvate is produced from glucose in the cytoplasm - pyruvate enters the mitochondria and is converted into citrate - citrate moves into the cytoplasm and is cleaved into acetyl CoA and oxaloactetate - acetyl CoA is converted into malonyl CoA - malonyl CoA is used to build fatty acids

Question 49

what enzyme converts Acetyl CoA into malonyl CoA

Answer 49

Acetyl-CoA carboxylase

Question 50

what enzyme complex uses malonyl CoA to produce fatty acids

Answer 50

fatty acid synthase complex

Question 51

where does fatty acid synthesis occur

Answer 51

cytoplasm

Question 52

true or false; only small amounts of energy are required in lipogenesis

Answer 52

false

Question 53

what enzyme regulates lipogenesis

Answer 53

acetyl-CoA carboxylase

Question 54

what hormone stimulates lipogenesis

Answer 54

insulin